The present invention relates to a circuit breaker used in a low voltage distribution circuit for a motor control or a wiring protection.
FIG. 37 is a front view of a conventional combination of a wiring circuit breaker and an electromagnetic switch. Referring now to FIG. 37, a motor circuit is protected by a combination of a wiring circuit breaker 110 and an electromagnetic switch 120. The load side terminals of the wiring circuit breaker 110 and the power supply side terminals of the electromagnetic switch 120 are connected phase by phase with conductors 130 (drawing shows three phases). FIG. 38 shows internal connections of the conventional circuit breaker and electromagnetic switch of FIG. 37. Referring now to FIG. 38, the wiring circuit breaker 110 includes contacts (hereinafter referred to as "first contacts") 111, and overcurrent trip devices 112, which are disposed for the respective phases for interrupting an overcurrent. The first contacts 111 are closed and opened by manually operating a breaker mechanism 113. The first contacts 111 are also opened by the breaker mechanism 113 based on a trip signal from the overcurrent trip device 112.
More in detail, when a handle 113a is turned under the state that the breaker mechanism 113 is reset where the latch is locked, an operation of an open-close spring to toggle links (not shown) is inverted to close or open the first contacts 111. When the latch is released by the trip signal from the overcurrent trip device 112, the breaker mechanism 113 releases the energy stored in the open-close spring to open the first contacts 111. The overcurrent trip device 112 includes a time delay trip portion 112a and an instantaneous trip portion 112b. The time delay trip portion 112a detects an overload current and feeds a trip signal to the breaker mechanism 113 after a period of time corresponding to the value of the overload current has passed. The instantaneous trip portion 112b detects a high current, such as a short-circuit current, and instantaneously feeds an instantaneous trip signal to the breaker mechanism 113.
In FIG. 38, the electromagnetic switch 120 includes contacts (hereinafter referred to as "second contacts) 121, thermal relays 122 and an electromagnet 123 for closing and opening the second contacts 121. When an overload current occurs, one of the thermal relays 122 breaks the control circuit of the electromagnet 123 to open the second contacts 121.
Since the conventional circuit breaker 110 and electromagnetic switch 120 are connected with each other with the conductors, a wiring space is necessary between the circuit breaker 110 and electromagnetic switch 120, and the wiring work is cumbersome. Since the circuit breaker 110 and electromagnetic switch 120 respectively include independent protecting means for protection from the overcurrent, both protecting means wastefully overlap in the overload protection region.
In view of the foregoing, the present invention has been made, and it is an object of the invention to provide a circuit breaker that does not need any wiring work between the first contacts and the second contacts.
It is another object of the invention to provide a circuit breaker as stated above, which avoids overlapping of the overcurrent protecting means of both contacts.